Liquid Crystal Composition  and Liquid Crystal Display Device

ABSTRACT

Subject The invention is to provide a liquid crystal composition that satisfies at least one characteristic among characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of a nematic phase, a small viscosity, a large optical anisotropy, a large dielectric anisotropy, a large specific resistance, a high stability to ultraviolet light and a high stability to heat, or that is suitably balanced regarding at least two of the characteristics. The invention is to provide an AM device that has a short response time, a large voltage holding ratio, a large contrast ratio, a long service life and so forth. 
     Means for Solving the Subject A liquid crystal composition having a nematic phase and containing a specific compound having a large optical anisotropy and a large dielectric anisotropy as a first component, and a specific compound having a small viscosity as a second component, and a liquid crystal display device contains this composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates mainly to a liquid crystal composition suitablefor use in an active matrix (AM) device, and an AM device containing thecomposition. More specifically, the invention relates to a liquidcrystal composition having a positive dielectric anisotropy, and adevice having a mode such as twisted nematic (TN), optically compensatedbend (OCB), IPS (in-plane switching) or PSA (polymer sustainedalignment), and containing the composition.

2. Related Art

In a liquid crystal display device, a classification based on anoperating mode for liquid crystals includes phase change (PC), twistednematic (TN), super twisted nematic (STN), electrically controlledbirefringence (ECB), optically compensated bend (OCB), in-planeswitching (IPS), vertical alignment (VA), and polymer sustainedalignment (PSA). A classification based on a driving mode in the deviceincludes a passive matrix (PM) and an active matrix (AM). The PM isfurther classified into static, multiplex and so forth, and the AM isclassified into a thin film transistor (TFT), a metal-insulator-metal(MIM) and so forth. The TFT is further classified into amorphous siliconand polycrystal silicon. The latter is classified into a hightemperature type and a low temperature type according to the productionprocess. A classification based on a light source includes a reflectiontype utilizing natural light, a transmission type utilizing a backlightand a semi-transmission type utilizing both natural light and abacklight.

These devices contain a liquid crystal composition having suitablecharacteristics. The liquid crystal composition has a nematic phase.General characteristics of the composition should be improved to give anAM device having good general characteristics. Table 1 below summarizesthe relationship between the general characteristics of the two. Thegeneral characteristics of the composition will be further explainedbased on a commercially available AM device. The temperature range of anematic phase relates to the temperature range in which the device canbe used. A desirable maximum temperature of the nematic phase isapproximately 70° C. or higher and a desirable minimum temperature ofthe nematic phase is approximately −10° C. or lower. The viscosity ofthe composition relates to the response time of the device. A shortresponse time is desirable to display moving images on the device.Accordingly, a small viscosity of the composition is desirable. A smallviscosity at a low temperature is more desirable.

TABLE 1 General Characteristics of a Liquid Crystal Composition and anAM Device General Characteristics of a General Characteristics ofComposition an AM Device Temperature range of a nematic Usabletemperature range is wide phase is wide Viscosity is small¹⁾ Responsetime is short Optical anisotropy is suitable Contrast ratio is largeDielectric anisotropy is positively Threshold voltage is low andelectric or negatively large power consumption is small Contrast ratiois large Specific resistance is large Voltage holding ratio is large anda contrast ratio is large It is stable to ultraviolet light and Servicelife is long heat ¹⁾A liquid crystal composition can be injected into aliquid crystal cell in a shorter period of time.

The optical anisotropy of the composition relates to the contrast ratioof the device. The product (Δn×d) of the optical anisotropy (Δn) of thecomposition and the cell gap (d) of the device is designed so as tomaximize the contrast ratio. A suitable value of the product depends onthe kinds of operating modes. A suitable value is in the range of about0.45 μm in such a device having a TN mode. In this case, a compositionhaving a large optical anisotropy is desirable for a device having asmall cell gap. A large dielectric anisotropy of the compositioncontributes to a low threshold voltage, a small electric powerconsumption and a large contrast ratio of the device. Accordingly, alarge dielectric anisotropy is desirable. A large specific resistance ofthe composition contributes to a large voltage holding ratio and a largecontrast ratio of the device. Accordingly, a composition having a largespecific resistance is desirable at room temperature and also at a hightemperature in the initial stage. A composition having a large specificresistance is desirable at room temperature and also at a temperatureclose to the maximum temperature of a nematic phase after it has beenused for a long time. The stability of the composition to ultravioletlight and heat relates to the service life of the liquid crystal displaydevice. In the case where the stability is high, the device has a longservice life. These characteristics are desirable for an AM device usedin a liquid crystal projector, a liquid crystal television and so forth.

A composition having a positive dielectric anisotropy is used for an AMdevice having a TN mode. On the other hand, a composition having anegative dielectric anisotropy is used for an AM device having a VAmode. A composition having a positive or negative dielectric anisotropyis used for an AM device having an IPS mode. A composition having apositive or negative dielectric anisotropy is used for an AM devicehaving a PSA mode. Examples of liquid crystal composition having apositive dielectric anisotropy are disclosed in the following patentdocuments Nos. 1 to 5.

Conventional compositions are disclosed in the following patentdocuments. No. 1: JP H9-77692 A (1997); No. 2: JP H10-46150 A (1998);No. 3: JP H10-114690 A (1998); No. 4: JP 2003-518154 A (2003); and No.5: JP 2007-526931 A (2007).

A desirable AM device has characteristics such as a wide temperaturerange in which the device can be used, a short response time, a largecontrast ratio, a low threshold voltage, a large voltage holding ratioand a long service life. Even one millisecond shorter response time isdesirable. Thus, a composition having characteristics such as a highmaximum temperature of a nematic phase, a low minimum temperature of anematic phase, a small viscosity, a large optical anisotropy, a largedielectric anisotropy, a large specific resistance, a high stability toultraviolet light and a high stability to heat is especially desirable.

SUMMARY OF THE INVENTION

The invention concerns a liquid crystal composition having a nematicphase that includes at least one compound selected from the group ofcompounds represented by formula (1) as a first component and at leastone compound selected from the group of compounds represented by formula(2) as a second component, and concerns a liquid crystal display deviceincluding the composition:

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; R² and R³are each independently alkenyl having 2 to 12 carbons; ring A and ring Bare each independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z¹ and Z² are eachindependently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹, X², X³ and X⁴ are each independently hydrogenor fluorine; Y¹ is fluorine, chlorine or trifluoromethoxy; and m and jare each independently 0, 1, 2 or 3 and the sum of m and j is 2 or 3.

DETAILED DESCRIPTION OF THE INVENTION

The terms used in the specification and claims are defined as follows.The liquid crystal composition and the liquid crystal display device ofthe invention may occasionally be abbreviated to “the composition” and“the device,” respectively. A liquid crystal display device is a genericterm for a liquid crystal display panel and a liquid crystal displaymodule. The “liquid crystal compound” is a generic term for a compoundhaving a liquid crystal phase such as a nematic phase and a smecticphase, and also for a compound having no liquid crystal phases but beinguseful as a component of a composition. The useful compound has asix-membered ring such as 1,4-cyclohexylene and 1,4-phenylene, and arod-like molecular structure. An optically active compound and apolymerizable compound may occasionally be added to the composition.Even in the case where these compounds are liquid crystal compounds, thecompounds are classified as an additive herein. At least one compoundselected from the group of compounds represented by formula (1) mayoccasionally be abbreviated to “the compound (1).” “The compound (1)”means one compound, or two or more compounds represented by formula (1).The same rules apply to compounds represented by the other formulas.“Arbitrary” is used not only in cases when the position is arbitrary butalso in cases when the number is arbitrary. However, it is not used incases when the number is 0 (zero).

A higher limit of the temperature range of a nematic phase mayoccasionally be abbreviated to “the maximum temperature.” A lower limitof the temperature range of a nematic phase may occasionally beabbreviated to “the minimum temperature.” That “a specific resistance islarge” means that a composition has a large specific resistance at roomtemperature and also at a temperature close to the maximum temperatureof a nematic phase in the initial stage, and that the composition has alarge specific resistance at room temperature and also at a temperatureclose to the maximum temperature of a nematic phase even after it hasbeen used for a long time. That “a voltage holding ratio is large” meansthat a device has a large voltage holding ratio at room temperature andalso at a temperature close to the maximum temperature of a nematicphase in the initial stage, and that the device has a large voltageholding ratio at room temperature and also at a temperature close to themaximum temperature of a nematic phase even after it has been used for along time. When characteristics such as optical anisotropy areexplained, values which are obtained according to the measuring methodsdescribed in Examples will be used. A first component means onecompound, or two or more compounds. “The ratio of the first component”means the percentage by weight (% by weight) of the first componentbased on the total weight of the liquid crystal composition. The samerule applies to the ratio of a second component and so forth. The ratioof an additive mixed into the composition means the percentage by weight(% by weight) or weight parts per million (ppm) based on the totalweight of the liquid crystal composition.

The symbol R¹ is used for a plurality of compounds in the chemicalformulas of component compounds. The meanings of two arbitrary R¹ may beidentical or different in these compounds. In one case, for example, R¹of the compound (1-1) is ethyl and R¹ of the compound (1-2) is ethyl. Inanother case, R¹ of the compound (1-1) is ethyl and R¹ of the compound(1-2) is propyl. The same rule applies to the symbols R², X¹ and soforth.

One of the advantages of the invention is to provide a liquid crystalcomposition that satisfies at least one characteristic amongcharacteristics such as a high maximum temperature of a nematic phase, alow minimum temperature of a nematic phase, a small viscosity, a largeoptical anisotropy, a large dielectric anisotropy, a large specificresistance, a high stability to ultraviolet light, and a high stabilityto heat. Another advantage of the invention is to provide a liquidcrystal composition that is suitably balanced regarding at least two ofthe characteristics. A further advantage of the invention is to providea liquid crystal display device that contains the liquid crystalcomposition. An additional advantage of the invention is to provide aliquid crystal composition that has a large optical anisotropy, a largedielectric anisotropy, a high stability to ultraviolet light and soforth, and is to provide an AM device that has a short response time, alarge voltage holding ratio, a large contrast ratio, a long service lifeand so forth.

The liquid crystal composition of the invention satisfied at least onecharacteristic among characteristics such as a high maximum temperatureof a nematic phase, a low minimum temperature of a nematic phase, asmall viscosity, a large optical anisotropy, a large dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat. The liquid crystal composition wassuitably balanced regarding at least two characteristics. The liquidcrystal display device contained the liquid crystal composition. Theliquid crystal composition had a large optical anisotropy, a largedielectric anisotropy, a high stability to ultraviolet light and soforth, and the AM device had a short response time, a large voltageholding ratio, a large contrast ratio, a long service life and so forth.

The invention includes the following items.

Item 1. A liquid crystal composition having a nematic phase thatincludes two components, wherein the first component is at least onecompound selected from the group of compounds represented by formula(1), and the second component is at least one compound selected from thegroup of compounds represented by formula (2):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; R² and R³are each independently alkenyl having 2 to 12 carbons; ring A and ring Bare each independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z¹ and Z² are eachindependently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹, X², X³ and X⁴ are each independently hydrogenor fluorine; Y¹ is fluorine, chlorine or trifluoromethoxy; and m and jare each independently 0, 1, 2 or 3 and the sum of m and j is 2 or 3.Item 2. The liquid crystal composition according to item 1, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formulas (1-1) to (1-9):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; X¹, X², X³,X⁴, X⁵, X⁶, X⁷, X⁸ and X⁹ are each independently hydrogen or fluorine;and Y¹ is fluorine, chlorine or trifluoromethoxy.Item 3. The liquid crystal composition according to item 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-1).Item 4. The liquid crystal composition according to item 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-2).Item 5. The liquid crystal composition according to item 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-5).Item 6. The liquid crystal composition according to item 2, wherein thefirst component is at least one compound selected from the group ofcompounds represented by formula (1-8).Item 7. The liquid crystal composition according to item 2, wherein thefirst component is a mixture of at least one compound selected from thegroup of compounds represented by formula (1-1) and at least onecompound selected from the group of compounds represented by formula(1-2).Item 8. The liquid Crystal composition according to any one of items 1to 7, wherein the ratio of the first component is in the range ofapproximately 5% to approximately 40% by weight and the ratio of thesecond component is in the range of approximately 20% to approximately95% by weight, based on the total weight of the liquid crystalcomposition.Item 9. The liquid crystal composition according to any one of items 1to 8, wherein the composition further includes at least one compoundselected from the group of compounds represented by formula (3) as athird component:

wherein R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; R⁵ is alkylhaving 1 to 12 carbons or alkoxy having 1 to 12 carbons; ring C and ringD are each independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z³ is independently a single bond, ethyleneor carbonyloxy; and p is 1, 2 or 3.Item 10. The liquid crystal composition according to item 9, wherein thethird component is at least one compound selected from the group ofcompounds represented by formulas (3-1) to (3-11):

wherein R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; and R⁵ isalkyl having 1 to 12 carbons or alkoxy having 1 to 12 carbons.Item 11. The liquid crystal composition according to item 10, whereinthe third component is at least one compound selected from the group ofcompounds represented by formula (3-1).Item 12. The liquid crystal composition according to item 10, whereinthe third component is a mixture of at least one compound selected fromthe group of compounds represented by formula (3-1) and at least onecompound selected from the group of compounds represented by formula(3-5).Item 13. The liquid crystal composition according to item 10, whereinthe third component is a mixture of at least one compound selected fromthe group of compounds represented by formula (3-1) and at least onecompound selected from the group of compounds represented by formula(3-7).Item 14. The liquid crystal composition according to item 10, whereinthe third component is a mixture of at least one compound selected fromthe group of compounds represented by formula (3-1) and at least onecompound selected from the group of compounds represented by formula(3-5) and at least one compound selected from the group of compoundsrepresented by formula (3-7).Item 15. The liquid crystal composition according to any one of items 9to 14, wherein the ratio of the third component is in the range ofapproximately 5% to approximately 60% by weight based on the totalweight of the liquid crystal composition.Item 16. The liquid crystal composition according to any one of items 1to 15, wherein the composition further includes at least one compoundselected from the group of compounds represented by formula (4) as afourth component:

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; ring E isindependently 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z⁴ is independently asingle bond, ethylene, carbonyloxy or difluoromethyleneoxy; X¹ and X²are each independently hydrogen or fluorine; Y¹ is fluorine, chlorine ortrifluoromethoxy; and k is 1 or 2.Item 17. The liquid crystal composition according to item 16, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formulas (4-1) to (4-18):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.Item 18. The liquid crystal composition according to item 17, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formula (4-10).Item 19. The liquid crystal composition according to item 17, whereinthe fourth component is at least one compound selected from the group ofcompounds represented by formula (4-11).Item 20. The liquid crystal composition according to item 17, whereinthe fourth component is a mixture of at least one compound selected fromthe group of compounds represented by formula (4-6) and at least onecompound selected from the group of compounds represented by formula(4-11).Item 21. The liquid crystal composition according to item 17, whereinthe fourth component is a mixture of at least one compound selected fromthe group of compounds represented by formula (4-10) and at least onecompound selected from the group of compounds represented by formula(4-11).Item 22. The liquid crystal composition according to any one of items 16to 21, wherein the ratio of the fourth component is in the range ofapproximately 5% to approximately 40% by weight based on the totalweight of the liquid crystal composition.Item 23. The liquid crystal composition according to any one of items 1to 22, wherein the maximum temperature of a nematic phase isapproximately 70° C. or higher, the optical anisotropy (25° C.) at awavelength of 589 nm is approximately 0.08 or more, and the dielectricanisotropy (25° C.) at a frequency of 1 kHz is approximately 2 or more.Item 24. A liquid crystal display device including the liquid crystalcomposition according to any one of items 1 to 23.Item 25. The liquid crystal display device according to item 24, whereinan operating mode of the liquid crystal display device is a TN mode, anOCB mode, an IPS mode or a PSA mode, and a driving mode of the liquidcrystal display device is an active matrix mode.

The invention further includes the following items: (1) the compositiondescribed above that further includes an optically active compound; (2)the composition described above that further includes an additive suchas an antioxidant, an ultraviolet light absorbent, an antifoaming agent,a polymerizable compound and/or a polymerization initiator; (3) an AMdevice that includes the composition described above; (4) a devicehaving a mode of TN, BCE, OCB, IPS or PSA and including the compositiondescribed above; (5) a device having a transmission type and includingthe composition described above; (6) use of the composition describedabove as a composition having a nematic phase; and (7) use as anoptically active composition by adding an optically active compound tothe composition described above.

The composition of the invention will be explained in the followingorder. First, the constitution of component compounds in the compositionwill be explained. Second, main characteristics of the componentcompounds and main effects of the compounds on the composition will beexplained. Third, a combination of components in the composition,desirable ratios of the component compounds and the basis thereof willbe explained. Fourth, a desirable embodiment of the component compoundswill be explained. Fifth, examples of the component compounds will beshown. Sixth, additives that may be mixed into the composition will beexplained. Seventh, methods for synthesizing the component compound willbe explained. Last, use of the composition will be explained.

First, the constitution of component compounds in the composition willbe explained. The composition of the invention is classified into thecomposition A and the composition B. The composition A may furthercontain other liquid crystal compounds, an additive, an impurity and soforth. “The other liquid crystal compounds” are different from thecompound (1), the compound (2), the compound (3) and the compound (4).Such compounds are mixed into the composition for the purpose of furtheradjusting characteristics of the composition. Of the other liquidcrystal compounds, a smaller amount of a cyano compound is moredesirable in view of its stability to heat or ultraviolet light. A moredesirable ratio of the cyano compound is approximately 0% by weight. Theadditive includes an optically active compound, an antioxidant, anultraviolet light absorbent, a coloring matter, an antifoaming agent, apolymerizable compound, and a polymerization initiator. The impurity isa compound and so forth contaminated in a process such as the synthesisof component compounds. Even in the case where the compound is liquidcrystalline, it is classified as an impurity herein.

The composition B is essentially consisting of compounds selected fromthe group of the compound (1), the compound (2), the compound (3) andthe compound (4). The term “essentially” means that the composition maycontain an additive and an impurity, but does not contain the otherliquid crystal compounds which are different from these compounds. Thecomposition B has a smaller number of components than the composition A.The composition B is preferable to the composition A in view of costreduction. The composition A is preferable to the composition B in viewof the fact that physical properties can be further adjusted by mixingthe other liquid crystal compounds.

Second, main characteristics of the component compounds and main effectsof the compounds on the composition will be explained. The maincharacteristics of the component compounds are summarized in Table 2 onthe basis of the effects of the invention. In Table 2, the symbol Lstands for “large” or “high”, the symbol M stands for “medium”, and thesymbol S stands for “small” or “low.” The symbols L, M and S areclassified on the basis of a qualitative comparison among the componentcompounds, and 0 (zero) means that “a value is nearly zero.”

TABLE 2 Characteristics of Compounds Compounds Compound CompoundCompound (1) Compound (2) (3) (4) Maximum M-L S-M S-L S-M temperatureViscosity M-L S S-M M-L Optical M-L S S-L M-L Anisotropy Dielectric M-L0 0 S-L Anisotropy Specific L L L L Resistance

Main effects of the component compounds on the characteristics of thecomposition upon mixing the component compounds to the composition areas follows. The compound (1) increases the optical anisotropy andincreases the dielectric anisotropy. The compound (2) decreases theviscosity. The compound (3) increases the maximum temperature ordecreases the minimum temperature. The compound (4) decreases theminimum temperature and increases the dielectric anisotropy.

Third, a combination of the components in the composition, desirableratios of the component compounds and the basis thereof will beexplained. The combination of the components in the composition is thefirst and second components, the first, second and third components, thefirst, second and fourth components, and the first, second, third andfourth components. A desirable combination of components in thecomposition are the first, second and third components, and the first,second, third and fourth components.

A desirable ratio of the first component is approximately 5% by weightor more for increasing the optical anisotropy and increasing thedielectric anisotropy, and is approximately 40% by weight or less fordecreasing the minimum temperature. A more desirable ratio is in therange of approximately 5% to approximately 30% by weight. An especiallydesirable ratio is in the range of approximately 5% to approximately 20%by, weight.

A desirable ratio of the second component is approximately 20% by weightor more for decreasing the viscosity, and is approximately 95% by weightor less for increasing the dielectric anisotropy. A more desirable ratiois in the range of approximately 25% to approximately 80% by weight. Anespecially desirable ratio is in the range of approximately 30% toapproximately 70% by weight.

A desirable ratio of the third component is approximately 5% by weightor more for increasing the maximum temperature or decreasing theviscosity, and is approximately 60% by weight or less for increasing thedielectric anisotropy. A more desirable ratio is in the range ofapproximately 10% to approximately 55% by weight. An especiallydesirable ratio is in the range of approximately 15% to approximately50% by weight.

The fourth component is suitable for the preparation of a compositionhaving especially large the dielectric anisotropy. A desirable ratio ofthis component is in the range of approximately 5% by weight to 40 byweight. A more desirable ratio is in the range of approximately 5% byweight to 35 by weight. An especially desirable ratio is in the range ofapproximately 5% to approximately 30% by weight.

Fourth, a desirable embodiment of the component compounds will beexplained. R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine. DesirableR¹ is alkyl having 1 to 12 carbons for increasing the stability toultraviolet light or heat. R² and R³ are each independently alkenylhaving 2 to 12 carbons. R⁴ is alkyl having 1 to 12 carbons, alkoxyhaving 1 to 12 carbons, alkenyl having 2 to 12 carbons, or alkenylhaving 2 to 12 carbons in which arbitrary hydrogen is replaced byfluorine. Desirable R⁴ is alkenyl having 2 to 12 carbons for decreasingthe minimum temperature. R⁵ is alkyl having 1 to 12 carbons or alkoxyhaving 1 to 12 carbons. Desirable R⁵ is alkyl having 1 to 12 carbons forincreasing the stability to ultraviolet light or heat.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptylor octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl or heptylfor decreasing the viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy or heptyloxy. More desirable alkoxy is methoxy or ethoxy fordecreasing the viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. More desirablealkenyl is vinyl, 1-propenyl, 3-butenyl or 3-pentenyl for decreasing theviscosity. A desirable configuration of —CH═CH— in the alkenyl dependson the position of the double bond. Trans is preferable in the alkenylsuch as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl and3-hexenyl for decreasing the viscosity and for something. C ispreferable in the alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl.In the alkenyl, straight-chain alkenyl is preferable to branched-chainalkenyl.

Desirable examples of alkenyl in which arbitrary hydrogen is replaced byfluorine are 2,2-difluorovinyl, 3,3-difluoro-2-propenyl,4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl and6,6-difluoro-5-hexenyl. More desirable examples are 2,2-difluorovinyland 4,4-difluoro-3-butenyl for decreasing the viscosity.

Ring A and ring B are each independently 1,4-cyclohexylene,1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl, and two arbitraryring A among these may be identical or different when m is 2 or 3, andtwo arbitrary ring B among these may be identical or different when j is2 or 3. Desirable ring A or ring B is 1,4-phenylene for increasing theoptical anisotropy. Ring C and ring D are each independently1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene,3-fluoro-1,4-phenylene or 2,5-difluoro-1,4-phenylene, and two arbitraryring C among these may be identical or different when p is 2 or 3.Desirable ring C or ring D is 1,4-cyclohexylene for decreasing theviscosity and 1,4-phenylene for increasing the optical anisotropy. RingE is independently 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl,1,4-phenylene, 2-fluoro-1,4-phenylene 3-fluoro-1,4-phenylene3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl, and two arbitraryring E may be identical or different when k is 2. Desirable ring E is1,4-phenylene for increasing the optical anisotropy.

Z¹, Z² and Z⁴ are each independently a single bond, ethylene,carbonyloxy or difluoromethyleneoxy, and two arbitrary Z¹ among thesemay be identical or different when m is 2 or 3 and two arbitrary Z²among these may be identical or different when j is 2 or 3 and twoarbitrary Z⁴ may be identical or different when k is 2. Desirable Z¹ orZ² is a single bond for decreasing the viscosity. Desirable Z⁴ isdifluoromethyleneoxy for increasing the dielectric anisotropy. Z³ isindependently a single bond, ethylene, or carbonyloxy, and two arbitraryZ³ among these may be identical or different when p is 2 or 3. DesirableZ³ is a single bond for decreasing the viscosity.

X¹, X², X³, X⁴, X⁵, X⁶, X⁷, X⁸, and X⁹ are each independently hydrogenor fluorine, and preferably at least two of X¹, X², X³, X⁴, X⁵, X⁶, X⁷,X⁸ and X⁹ have fluorine for increasing the dielectric anisotropy.

Y¹ is fluorine, chlorine or trifluoromethoxy. Desirable Y¹ is fluorinefor decreasing the minimum temperature.

m and j are each independently 0, 1, 2 or 3 and the sum of m and j is 3or less. Desirable m is 2 for increasing the maximum temperature.Desirable j is 0 for decreasing the minimum temperature. p is 1, 2 or 3.Desirable p is 1 for decreasing the viscosity. k is 1 or 2. Desirable kis 2 for decreasing the minimum temperature.

Fifth, examples of the component compounds will be shown. In thedesirable compounds described below, R⁶ is straight-chain alkyl having 1to 12 carbons. R⁷ is straight-chain alkyl having 1 to 12 carbons orstraight-chain alkoxy having 1 to 12 carbons. R⁸ is straight-chain alkylhaving 1 to 12 carbons or straight-chain alkenyl having 2 to 12 carbons.R⁹ and R¹⁰ are each independently straight-chain alkenyl having 2 to 12carbons. With regard to the configuration of 1,4-cyclohexylene in theseCompounds, trans is preferable to cis for increasing the maximumtemperature.

Desirable compound (1) are the compounds (1-1-1) to (1-1-3), thecompounds (1-2-1) to (1-2-3), the compounds (1-3-1) to (1-3-2), thecompounds (1-4-1) to (1-4-2), the compounds (1-5-1) to (1-5-3), thecompounds (1-6-1) to (1-6-2), the compounds (1-7-1) to (1-7-2), thecompounds (1-8-1) to the compound (1-8-2) and the compound (1-9-1). Moredesirable compound (1) are the compound (1-1-1), the compound (1-1-2),the compound (1-1-3), the compound (1-2-3), the compound (1-4-2), thecompound (1-5-3), the compound (1-6-2), the compound (1-7-2) and thecompound (1-8-2). Especially desirable compound (1) are the compound(1-1-1), the compound (1-1-2), the compound (1-1-3), the compound(1-2-3) and the compound (1-8-2). Desirable compound (2) is the compound(2-1-1). Desirable compound (3) are the compounds (3-1-1) to (3-11-1).More desirable compound (3) are the compound (3-1-1), the compound(3-3-1), the Compound (3-5-1), the compound (3-7-1), the compound(3-8-1) and the compound (3-11-1). Especially desirable compound (3) arethe compound (3-1-1), the compound (3-5-1), the compound (3-7-1) and thecompound (3-11-1). Desirable compound (4) are the compounds (4-1-1) to(4-18-1). More desirable compound (4) are the compound (4-6-1), thecompound (4-9-1), the compound (4-10-1), the compound (4-11-1) and thecompound (4-12-1). Especially desirable compound (4) are the compound(4-6-1), the compound (4-9-1), the compound (4-10-1) and the compound(4-11-1).

Sixth, additives which may be mixed into the composition will beexplained. The additives include an optically active compound, anantioxidant, an ultraviolet light absorbent, a coloring matter, anantifoaming agent, a polymerizable compound and a polymerizationinitiator. The optically active compound is mixed into the compositionfor the purpose of inducing a helical structure and giving a twist anglein liquid crystals. Examples of the optically active compound includethe compounds (5-1) to (5-4) below. A desirable ratio of the opticallyactive compound is approximately 5% by weight or less, and a moredesirable ratio is in the range of approximately 0.01% to approximately2% by weight.

An antioxidant is mixed into the composition in order to prevent adecrease in specific resistance Caused by heating in air, or to maintaina large voltage holding ratio at room temperature and also at atemperature close to the maximum temperature of a nematic phase evenafter the device has been used for a long time.

Desirable examples of the antioxidant include the compound (6) wherein nis an integer of from 1 to 9. In the compound (6), desirable n is 1, 3,5, 7 or 9. More desirable n is 1 or 7. The compound (6) wherein n is 1,is effective in preventing a decrease of the specific resistance causedby heating in air because it has a large volatility. The compound (6)wherein n is 7 is effective in maintaining a large voltage holding ratioat room temperature and also at a temperature close to the maximumtemperature of a nematic phase even after the device has been used for along time, because it has a small volatility. A desirable ratio of theantioxidant is approximately 50 ppm or more for achieving its effect andis approximately 600 ppm or less for avoiding a decrease of the maximumtemperature or avoiding an increase of the minimum temperature. A moredesirable ratio is in the range of approximately 100 ppm toapproximately 300 ppm.

Desirable examples of the ultraviolet light absorbent include abenzophenone derivative, a benzoate derivative and a triazolederivative. A light stabilizer such as an amine having steric hindranceis also desirable. A desirable ratio of the ultraviolet light absorbentand the light stabilizer is approximately 50 ppm or more for achievingits effect and is approximately 10,000 ppm or less for avoiding adecrease of the maximum temperature or avoiding an increase of theminimum temperature. A more desirable ratio is in the range ofapproximately 100 ppm to approximately 10,000 ppm.

A dichroic dye such as an azo dye or an anthraquinone dye is mixed intothe composition for adjusting to a device having a guest host (GH) mode.A desirable ratio of the coloring matter is in the range ofapproximately 0.01% to approximately 10% by weight. An antifoaming agentsuch as dimethyl silicone oil or methyl phenyl silicone oil is mixedinto the composition for preventing foam formation. A desirable ratio ofthe antifoaming agent is approximately 1 ppm or more for achieving itseffect and is approximately 1,000 ppm or less for avoiding a poordisplay. A more desirable ratio is in the range of approximately 1 ppmto approximately 500 ppm.

A polymerizable compound is mixed into the composition for adjusting toa device having a PSA (polymer sustained alignment) mode. Desirableexamples of the polymerizable compound include compounds having apolymerizable group, such as acrylates, methacrylates, vinyl compounds,vinyloxy compounds, propenyl ethers, epoxy compounds (oxirane, oxetane)and vinyl ketones. Especially desirable examples of the polymerizablecompound are acrylate derivatives or methacrylate derivatives. Adesirable ratio of the polymerizable compound is approximately 0.05% byweight or more for achieving its effect and is approximately 10% byweight or less for avoiding a poor display. Amore desirable ratio is inthe range of approximately 0.1% to approximately 2% by weight. Thepolymerizable compound is preferably polymerized on irradiation withultraviolet light or the like in the presence of a suitable initiatorsuch as a photoinitiator. Suitable conditions for polymerization,suitable types of the initiator and suitable amounts thereof are knownto a person skilled in the art and are described in the literature. Forexample, Irgacure 651 (registered trademark), Irgacure 184 (registeredtrademark) or Darocure 1173 (registered trademark) (Ciba Japan K.K.),which is a photopolymerization initiator, is suitable for radicalpolymerization. The polymerizable compound includes thephotopolymerization initiator preferably in the range of approximately0.1% to approximately 5% by weight, and most preferably in the range ofapproximately 1% to approximately 3% by weight.

Seventh, methods for synthesizing the component compounds will beexplained. These compounds can be synthesized by known methods. Thesynthetic methods will be exemplified as follows. The compound (1-2-3)is synthesized by the method described in JP H10-251186 A (1998). Thecompound (2-1-1) is synthesized by the method described in JP H9-77692 A(1997). The compound (3-5-1) is synthesized by the method described inJP S57-165328 A (1982) The compounds (4-5-1) and (4-8-1) are synthesizedby the method described in JP H2-233626 A (1990). An antioxidant iscommercially available. The compound of formula (6), wherein n is 1, isavailable from Sigma-Aldrich Corporation, The compound (6), wherein n is7, and so forth are synthesized according to the method described inU.S. Pat. No. 3,660,505.

The compounds that synthetic methods were not described above can besynthesized according to the methods described in books such as ORGANICSYNTHESES (John Wiley & Sons, Inc.), ORGANIC REACTIONS (John Wiley &Sons, Inc.), COMPREHENSIVE ORGANIC SYNTHESIS (Pergamon Press), and NEWEXPERIMENTAL CHEMISTRY COURSE (Shin Jikken Kagaku Kouza, in Japanesetitle) (Maruzen, Inc.). The composition is prepared according to knownmethods using the compounds thus obtained. For example, the componentcompounds are mixed and dissolved in each other by heating.

Last, use of the composition will be explained. The composition of thepresent invention mainly has a minimum temperature of approximately −10°C. or lower, a maximum temperature of approximately 70° C. or higher,and an optical anisotropy in the range of approximately 0.07 toapproximately 0.20. The device containing the composition has a largevoltage holding ratio. The composition is suitable for an AM device. Thecomposition is suitable especially for an AM device having atransmission type. The composition having an optical anisotropy in therange of approximately 0.08 to approximately 0.25 and additionally inthe range of approximately 0.10 to approximately 0.30 may be prepared byregulating ratios of the component compounds or by mixing other liquidcrystal compounds. The composition can be used as a composition having anematic phase and as an optically active composition by adding anoptically active compound.

The composition can be used for an AM device. It can also be used for aPM device. The composition can also be used for the AM device and the PMdevice having a mode such as PC, TN, STN, ECB, OCB, IPS, VA or PSA. Itis especially desirable to use the composition for the AM device havingthe TN, OCB or IPS mode. These devices may be of a reflection type, atransmission type or a semi-transmission type. It is desirable to usethe composition for a device having the transmission type. It can beused for an amorphous silicon-TFT device or a polycrystal silicon-TFTdevice. The composition is also usable for a nematic curvilinear alignedphase (NCAP) device prepared by microcapsulating the composition, andfor a polymer dispersed (PD) device in which a three-dimensionalnetwork-polymer is formed in the composition.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the invention and specificexamples provided herein without departing from the spirit or scope ofthe invention. Thus, it is intended that the invention covers themodifications and variations of this invention that come within thescope of any claims and their equivalents.

The following examples are for illustrative purposes only and are notintended, nor should they be interpreted to, limit the scope of theinvention.

EXAMPLES

A composition and a compound were a subject for measurement in order toevaluate the composition and the compound to be included in thecomposition. When the subject for measurement was a composition, thecomposition itself was measured as a sample, and the value obtained wasdescribed here. When the subject for measurement was a compound, asample for measurement was prepared by mixing the compound (15% byweight) and mother liquid crystals (85% by weight). Characteristicvalues of the compound were calculated from values obtained bymeasurement, according to a method of extrapolation. That is:(extrapolated value)=[(measured value of a sample formeasurement)−0.85×(measured value of mother liquid crystals)]/0.15. Whena smectic phase (or crystals) separated out at this ratio at 25° C., theratio of the compound and the mother liquid crystals was changed step bystep in the order of (10% by weight/90% by weight), (5% by weight/95% byweight), (1% by weight/99% by weight). Values of the maximumtemperature, the optical anisotropy, the viscosity and the dielectricanisotropy with regard to the compound were obtained by theextrapolation.

The components of the mother liquid crystals were as follows. The ratioof each component is expressed in percentage by weight.

Characteristics were measured according to the following methods. Mostmethods are described in the Standards of Electronic IndustriesAssociation of Japan, EIAJ•ED-2521 A or those with some modifications.

Maximum Temperature of a Nematic Phase (NI; ° C.): A sample was placedon a hot plate in a melting point apparatus equipped with a polarizingmicroscope and was heated at the rate of 1° C. per minute. Temperaturewas measured when part of the sample began to change from a nematicphase to an isotropic liquid. A higher limit of the temperature range ofa nematic phase may occasionally be abbreviated to “the maximumtemperature.”

Minimum Temperature of a Nematic Phase (Tc; ° C.): A sample having anematic phase was put in glass vials and then kept in freezers attemperatures of 0° C., −10° C., −20° C., −30° C. and −40° C. for 10days, and then the liquid crystal phases were observed. For example,when the sample remained the nematic phase at −20° C. and changed tocrystals or a smectic phase at −30° C., Tc was expressed as ≦−20° C. Alower limit of the temperature range of a nematic phase may occasionallybe abbreviated to “the minimum temperature.”

Viscosity (bulk viscosity; η; measured at 20° C.; mPa·s): Viscosity wasmeasured by use of an E-type viscometer.

Viscosity (rotational viscosity; γ1; measured at 25° C.; mPa·s):Measurement was carried out according to the method described in M.Imai, et al., Molecular Crystals and Liquid Crystals, Vol. 259, 37(1995). A sample was poured into a TN device having the twist angle of 0degrees and the distance between two glass substrates (cell gap) of 5μm. The TN device was impressed with a voltage stepwise with anincrement of 0.5 volt in the range of 16 to 19.5 volts. After a periodof 0.2 second without impressed voltage, voltage impress was repeatedunder the conditions of only one rectangular wave (rectangular pulse;0.2 second) and no voltage impressed (2 seconds). The peak current andthe peak time of the transient current generated by the voltageimpressed were measured. The value of rotational viscosity was obtainedfrom the measured values and the calculating equation (8) in page 40 ofthe paper presented by M. Imai, et al. The value of dielectricanisotropy necessary for this calculation was obtained by use of thedevice that had been used for the present measurement of rotationalviscosity, according to the method that will be described below.

Optical Anisotropy (refractive index anisotropy; Δn; measured at 25°C.): Measurement was carried out by use of an Abbe refractometer with apolarizing plate mounted on the ocular, on irradiation with light at awavelength of 589 nm. The surface of the main prism was rubbed in onedirection, and then a sample was dropped on the main prism. A refractiveindex (n∥) was measured when the direction of polarized light wasparallel to that of the rubbing. A refractive index (n⊥) was measuredwhen the direction of polarized light was perpendicular to that of therubbing. The value of optical anisotropy was calculated from theequation: Δn=n∥−n⊥.

Dielectric Anisotropy (Δ∈; measured at ° C.): A sample was poured into aTN device having the distance between two glass plates (cell gap) of 9μm and the twist angle of 80°. Sine waves (10 V, 1 kHz) were impressedonto the device, and a dielectric constant (∈∥) in a major axisdirection of liquid crystal molecules was measured after 2 seconds. Sinewaves (0.5 V, 1 kHz) were impressed onto the device and a dielectricconstant (∈⊥) in a minor axis direction of liquid crystal molecules wasmeasured after 2 seconds. A value of the dielectric anisotropy wascalculated from the equation: Δ∈=∈∥−∈⊥.

Threshold Voltage (Vth; measured at 25° C.; V): Measurement was carriedout with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. A sample waspoured into a TN device having a normally white mode, in which thedistance between two glass substrates (cell gap) was about 4.45/Δn (μm)and the twist angle was 80 degrees. Voltage to be impressed onto thedevice (32 Hz, rectangular waves) was stepwise increased in 0.02 Vincrements from 0 V up to 10 V. During the increase, the device wasirradiated with light in the perpendicular direction, and the amount oflight passing through the device was measured. A voltage-transmittancecurve was prepared, in which the maximum amount of light corresponded to100% transmittance and the minimum amount of light corresponded to 0%transmittance. The threshold voltage was voltage at 90% transmittance.

Voltage Holding Ratio (VHR-1; measured at 25° C.; %): A TN device usedfor measurement had a polyimide-alignment film, and the distance betweentwo glass substrates (cell gap) was 5 μm. A sample was poured into thedevice, and then the device was sealed with an adhesive curable onirradiation with ultraviolet light. The device was impressed and chargedwith pulse voltage (60 microseconds at 5 V). A decreasing voltage wasmeasured for 16.7 milliseconds with a high-speed voltmeter, and the areaA between a voltage curve and a horizontal axis in a unit cycle wasobtained. The area B was an area without the decrease. The voltageholding ratio was a percentage of the area A to the area B.

Voltage Holding Ratio (VHR-2; measured at 80° C.; %): A TN device usedfor measurement had a polyimide-alignment film, and the distance betweentwo glass substrates (cell gap) was 5 μm. A sample was poured into thedevice, and then the device was sealed with an adhesive curable onirradiation with ultraviolet light. The TN device was impressed andcharged with pulse voltage (60 microseconds at 5 V). A decreasingvoltage was measured for 16.7 milliseconds with a high-speed voltmeterand the area A between a voltage curve and a horizontal axis in a unitcycle was obtained. The area B was an area without the decease. Thevoltage holding ratio was a percentage of the area A to the area B.

Voltage Holding Ratio (VHR-3; measured at 25° C.; %): A voltage holdingratio was measured after irradiation with ultraviolet light, evaluatingthe stability to ultraviolet light. A composition having a large VHR-3has a high stability to ultraviolet light. A TN device used formeasurement had a polyimide-alignment film and the cell gap was 5 μm. Asample was poured into the device, and then the device was irradiatedwith light for 20 minutes. The light source was an ultra high-pressuremercury lamp USH-500D (produced by Ushio, Inc.), and the distancebetween the device and the light source was 20 cm. In the measurement ofVHR-3, a decreasing voltage was measured for 16.7 milliseconds. Thevalue of VHR-3 is preferably 90% or more, and more preferably 95% ormore.

Voltage Holding Ratio (VHR-4; measured at 25° C.; %): A TN device intowhich a sample was poured was heated in a constant-temperature bath at80° C. for 500 hours, and then the Voltage holding ratio was measured,evaluating the stability to heat. A composition having a large VHR-4 hasa high stability to heat. In the measurement of VHR-4, a decreasingvoltage was measured for 16.7 milliseconds.

Response Time (τ; measured at 25° C.; millisecond): Measurement wascarried out with an LCD evaluation system Model LCD-5100 made by OtsukaElectronics Co., Ltd. The light source was a halogen lamp. The low-passfilter was set at 5 kHz. A sample was poured into a TN device having anormally white mode, in which the cell gap between two glass substrateswas 5.0 μm, and the twist angle was 80 degrees. Rectangular waves (60Hz, 10 V, 0.5 second) were impressed to the device. The device wassimultaneously irradiated with light in the perpendicular direction, andthe amount of light passing through the device was measured. The maximumamount of light corresponded to 100% transmittance, and the minimumamount of light corresponded to 0% transmittance. Rise time (τr;millisecond) was the time required for a change from 90% to 10%transmittance. Fall time (τf; millisecond) was the time required for achange from 10% to 90% transmittance. The response time was the sum ofthe rise time and the fall time thus obtained.

Specific resistance (ρ; measured at 25° C.; Ωcm): A sample of 1.0milliliters was poured into a vessel equipped with electrodes. DCvoltage (10V) was impressed to the vessel, and the DC current wasmeasured after 10 seconds. The specific resistance was calculatedaccording to the following equation. (specificresistance)=[(voltage)×(electric capacity of vessel)]/[(DCcurrent)×(dielectric constant in a vacuum)].

Gas chromatographic analysis: A gas chromatograph Model GC-14B made byShimadzu Corporation was used for measurement. The carrier gas washelium (2 milliliters per minute). The evaporator and the detector (FID)were set up at 280° C. and 300° C., respectively. A capillary columnDB-1 (length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer, dimethylpolysiloxane as the stationary phase, non-polar)made by Agilent Technologies, Inc. was used for the separation ofcomponent compounds. After the column had been kept at 200° C. for 2minutes, it was further heated to 280° C. at the rate of 5° C. perminute. A sample was prepared in an acetone solution (0.1% by weight),and 1 microliter of the solution was injected into the evaporator. Arecorder used was a Model C-R5A Chromatopac Integrator made by ShimadzuCorporation or its equivalent. A gas chromatogram obtained showed theretention time of peaks and the peak areas corresponding to thecomponent compounds.

Solvents for diluting the sample may also be chloroform, hexane and soforth. The following capillary columns may also be used in order toseparate the component compounds: HP-1 made by Agilent Technologies Inc.(length 30 meters, bore 0.32 millimeter, film thickness 0.25micrometer), Rtx-1 made by Restek Corporation (length 30 meters, bore0.32 millimeter, film thickness 0.25 micrometer), and BP-1 made by SGEInternational Pty. Ltd. (length 30 meters, bore 0.32 millimeter, filmthickness 0.25 micrometer). A capillary column CBP1-M50-025 (50 meters,bore 0.25 millimeter, film thickness 0.25 micrometer) made by ShimadzuCorporation may also be used for the purpose of avoiding an overlap ofpeaks of the compounds.

The ratio of the liquid crystal compounds included in the compositionmay be calculated according to the following method. The liquid crystalcompounds are detected by use of a gas chromatograph. The ratio of peakareas in the gas chromatogram corresponds to the ratio (in moles) of theliquid crystal compounds. When the capillary columns described above areused, the correction coefficient of respective liquid crystal compoundsmay be regarded as 1 (one). Accordingly, the ratio (percent by weight)of the liquid crystal compound can be calculated from the ratio of peakareas.

The invention will be explained in detail by way of Examples. Theinvention is not limited by Examples described below. The compoundsdescribed in Comparative Examples and Examples were expressed as symbolsaccording to the definition in the following Table 3. In Table 3, theconfiguration of 1,4-cyclohexylene is trans. A parenthesized number nextto the symbolized compound in Example corresponds to the compound'snumber. The symbol (−) means other liquid crystal compounds. Ratios(percentage) of liquid crystal compounds mean the percentages by weight(% by weight) based on the total weight of the liquid crystalcomposition. The liquid crystal composition further includes animpurity. Last, characteristics of the composition are summarized.

TABLE 3 Method of Description of Compound using Symbols R—(A₁)—Z₁— . . .—Z_(n)—(A_(n))—R′ 1) Left-terminal Group R— Symbol C_(n)H_(2n+1)— n—C_(n)H_(2n+1)O— nO— C_(m)H_(2m+1)OC_(n)H_(2n)— mOn— CH₂═CH— V—C_(n)H_(2n+1)CH═CH— nV— CH₂═CH—C_(n)H_(2n)— Vn—C_(m)H_(2m+1)—CH═CH—C_(n)H_(2n)— mVn— CF₂═CH— VFF— CF₂═CH—C_(n)H_(2n)—VFFn— 2) Right-teminal Group —R′ Symbol —C_(n)H_(2n+1) —n—OC_(n)H_(2n+1) —On —CH═CH₂ —V —CH═CH—C_(n)H_(2n+1) —Vn—C_(n)H_(2n)—CH═CH₂ —nV —CH═CF₂ —VFF —F —F —Cl —CL —OCF₃ —OCF3 —CN —C 3)Bonding Group —Z_(n)— Symbol —C₂H₄— 2 —COO— E —CH═CH— V —C≡C— T —CF₂O— X4) Ring Structure —A_(n)— Symbol

H

B

B(F)

B(2F)

B(F,F)

B(2F,5F)

Py

dh

G 5) Example of Description Example 1. 5-BB(F)B(F,F)XB(F)—OCF3

Example 2. V—HH—V

Example 3. 3-HHB-1

Example 4. 3-BB(F)B(F,F)—F

Comparative Example 1

The composition of Example 1 was selected from the compositionsdisclosed in JP H10-46150 A (1998) for comparison. The basis for theselection was because the composition contained the compound (2-1-1) andthe compound (4), and had the smallest viscosity. The composition hadthe following components and characteristics. Since rotational viscositywas not mentioned in Example 1, it was measured according to the methoddescribed above after the preparation of the composition.

V2-HH-2V (2-1-1) 30% V-HHB(F)-F (4) 35% V2-HHB(F)-F (4) 35% NI = 102.0°C.; Δn = 0.079; Δε = 3.0; Vth = 2.46 V; η = 12.9 mPa · s; γ1 = 56.4 mPa· s.

Comparative Example 2

The composition of Example 12 was selected from the compositionsdisclosed in JP 2003-518154 A (2003) for comparison. The basis for theselection was because the composition contained the compound (3-1-1),the compound (3-2-1), the compound (3-5-1), the compound (3-6-1), thecompound (3-9-1), the compound (4), the compound (4-10-1), the compound(4-11-1) and the compound (4-15-1), and had the smallest rotationalviscosity. The composition had the following components andcharacteristics.

V-HH-3 (3-1-1) 18% 1V-HH-3 (3-1-1) 9% 3-HH-5 (3-1-1) 3% V-HH-5 (3-1-1)2% 5-HB-3 (3-2-1) 2% 2-HHB-OCF3 (4) 2% 3-HHB-OCF3 (4) 6% 3-BB(F)B(F,F)-F(4-10-1) 7% 2-BB(F,F)XB(F,F)-F (4-11-1) 6% 3-BB(F,F)XB(F,F)-F (4-11-1)11% 3-HHEB(F,F)-F (4-15-1) 4% 3-HB(F)EB-OCF3 (4) 8% V-HHB(F)-F (4) 5%V-HHB-1 (3-5-1) 13% 5-HBBH-3 (3-9-1) 2% 3-HBB-2 (3-6-1) 2% NI = 80.0°C.; Δn = 0.102; Vth = 1.57 V; γ1 = 72.0 mPa · s.

Comparative Example 3

The composition of Example 21 was selected from the compositionsdisclosed in JP 2007-526931 A (2007) for comparison. The basis for theselection was because the composition contained the compound (2-1-1),the compound (3-1-1), the compound (3-7-1), the compound (4), thecompound (4-11-1) and the compound (4-15-1), and had the smallestrotational viscosity. The composition had the following components andcharacteristics.

2-HHB-OCF3 (4) 4% 3-HHB-OCF3 (4) 4% 3-HHEB(F,F)-F (4-15-1) 4%1-BB(F,F)XB(F,F)-F (4-11-1) 8% 2-BB(F,F)XB(F,F)-F (4-11-1) 8% 1V-HH-3(3-1-1) 6% 1V-HVHB-OCF3 (—) 14% 2V-HVHB-OCF3 (—) 4% 2-BB(F)B-4 (3-7-1)8% V-HH-V1 (2-1-1) 40% NI = 76.0° C.; Δε = 5.4; γ1 = 58.0 mPa · s.

Example 1

3-HBBXB(F,F)-F (1-1-1) 4% 5-BB(F,F)XB(F)B(F,F)-F (1-3-2) 4%5-BB(F)B(F)B(F,F)XB(F,F)-F (1-6-2) 3% 5-BB(F)B(F,F)XB(F)B(F,F)-F (1-8-2)7% V-HH-V (2-1-1) 15% V-HH-2V (2-1-1) 20% 1V-HH-V (2-1-1) 10% V-HH-3(3-1-1) 9% 3-HB-O2 (3-2-1) 6% V2-BB-1 (3-3-1) 5% V-HHB-1 (3-5-1) 8%1-BB(F)B-2V (3-7-1) 5% 2-BB(F)B-2V (3-7-1) 4% NI = 78.4° C.; Tc ≦ −20°C.; Δn = 0.110; Δε = 3.1; Vth = 2.50 V; η = 10.9 mPa · s; γ1 = 44.6 mPa· s; τ = 8.5 ms; VHR-1 = 99.1%; VHR-2 = 98.0%; VHR-3 = 98.1%.

Example 2

3-HBB(F,F)XB(F,F)-F (1-1-2) 7% 3-HB(F)B(F,F)XB(F,F)-F (1-1-3) 7% V-HH-2V(2-1-1) 20% V2-HH-2V (2-1-1) 10% 1V2-HH-V (2-1-1) 5% V-HH-3 (3-1-1) 15%V-HH-5 (3-1-1) 6% V2-HHB-1 (3-5-1) 6% 1V-HBB-2 (3-6-1) 3% 3-BB(F)B-2V(3-7-1) 5% 3-HHEBH-5 (3-8-1) 3% 3-HHB(F,F)-F (4-5-1) 3%3-BB(F,F)XB(F,F)-F (4-11-1) 10% NI = 75.1° C.; Tc ≦ −20° C.; Δn = 0.091;Δε = 3.2; Vth = 2.38 V; η = 11.8 mPa · s; γ1 = 46.8 mPa · s; τ = 8.7 ms;VHR-1 = 99.1%; VHR-2 = 98.0%; VHR-3 = 98.2%.

Example 3

5-BBB(F,F)XB(F,F)-F (1-2-1) 3% 4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 9%5-HHBB(F,F)XB(F,F)-F (1-4-1) 3% 5-PyB(F)B(F,F)XB(F)B(F,F)-F (1-9-1) 4%V-HH-V (2-1-1) 15% V-HH-2V (2-1-1) 20% 1V-HH-V (2-1-1) 10% 2-HH-3(3-1-1) 12% 1V-HH-3 (3-1-1) 8% 2-BB(F)B-3 (3-7-1) 5% 1V2-BB-CL (4-3-1)4% 5-HBB-F (4-7-1) 3% 2-HBB(F,F)-F (4-8-1) 4% NI = 71.3° C.; Tc ≦ −20°C.; Δn = 0.098; Δε = 3.1; Vth = 2.45 V; η = 11.7 mPa · s; γ1 = 46.6 mPa· s; τ = 8.7 ms; VHR-1 = 99.0%; VHR-2 = 98.0%; VHR-3 = 97.8%.

Example 4

5-HBB(F,F)XB(F)B(F,F)-F (1-7-1) 3% 5-HB(F)B(F,F)XB(F)B(F,F)-F (1-7-2) 3%V-HH-2V (2-1-1) 20% V2-HH-2V (2-1-1) 7% 1V2-HH-2V1 (2-1-1) 4% V-HH-3(3-1-1) 23% 3-HH-4 (3-1-1) 4% VFF-HHB-1 (3-5) 3% 3-HHB-O1 (3-5-1) 3%V2-HHB-1 (3-5-1) 6% 1-BB(F)B-2V (3-7-1) 4% 3-HHXB(F,F)-F (4-6-1) 3%3-BB(F)B(F,F)-F (4-10-1) 5% 3-BB(F,F)XB(F,F)-F (4-11-1) 12% NI = 70.2°C.; Tc ≦ −20° C.; Δn = 0.090; Δε = 2.8; Vth = 2.59 V; η = 11.0 mPa · s;γ1 = 45.0 mPa · s; τ = 8.5 ms; VHR-1 = 99.0%; VHR-2 = 98.1%; VHR-3 =98.1%.

Example 5

3-BB(F)B(F,F)XB(F)-OCF3 (1-2-2) 3% 4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 8%3-BB(F,F)XB(F,F)B(F)-OCF3 (1-3-1) 3% 5-BB(F)B(F,F)XB(F)B(F)-OCF3 (1-8-1)4% V-HH-V (2-1-1) 15% V-HH-2V (2-1-1) 20% 1V-HH-V1 (2-1-1) 5% 1V2-HH-V(2-1-1) 5% 3-HH-5 (3-1-1) 3% V-HH-3 (3-1-1) 7% 7-HB-1 (3-2-1) 4%1V2-BB-1 (3-3-1) 4% V2-HHB-1 (3-5-1) 8% 3-HBB-2 (3-6-1) 3% 5-HB(F)BH-3(3-10-1) 3% 3-BB(F,F)XB(F)-OCF3 (4-12-1) 5% NI = 75.3° C.; Tc ≦ −20° C.;Δn = 0.098; Δε = 2.7; Vth = 2.64 V; η = 11.9 mPa · s; γ1 = 47.7 mPa · s;τ = 8.9 ms; VHR-1 = 99.1%; VHR-2 = 98.0%; VHR-3 = 98.1%

Example 6

4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 9% 5-HHB(F)B(F,F)XB(F,F)-F (1-4-2) 3%5-HBBB(F,F)XB(F,F)-F (1-5-1) 3% V-HH-V (2-1-1) 10% V-HH-2V (2-1-1) 20%3-HH-VFF (3-1) 5% V-HH-3 (3-1-1) 24% V2-HHB-1 (3-5-1) 3% 2-BB(F)B-2V(3-7-1) 5% 5-HBBH-3 (3-9-1) 3% 3-HB-CL (4-1-1) 4% 3-HB(F)B(F,F)-F(4-9-1) 4% 3-BB(F,F)XB(F,F)-F (4-11-1) 7% NI = 71.2° C.; Tc ≦ −20° C.;Δn = 0.094; Δε = 3.2; Vth = 2.36 V; η = 11.8 mPa · s; γ1 = 47.4 mPa · s;τ = 8.8 ms; VHR-1 = 99.0%; VHR-2 = 98.1%; VHR-3 = 98.2%.

Example 7

4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 5% 5-HBB(F)B(F,F)XB(F,F)-F (1-5-2) 3%5-BB(F)B(F,F)XB(F)B(F,F)-F (1-8-2) 4% V-HH-V (2-1-1) 15% V-HH-2V (2-1-1)20% 1V-HH-V (2-1-1) 10% V-HH-3 (3-1-1) 12% 1V-HH-3 (3-1-1) 8% V-HHB-1(3-5-1) 5% 5-HBB(F)B-3 (3-11-1) 4% 3-BB(F,F)XB(F,F)-F (4-11-1) 7%3-HHXB(F)-OCF3 (4-13-1) 3% 3-BB(F,F)XB(F)-F (4-14-1) 4% NI = 72.0° C.;Tc ≦ −20° C.; Δn = 0.087; Δε = 2.8; Vth = 2.58 V; η = 11.5 mPa · s; γ1 =46.3 mPa · s; τ = 8.7 ms; VHR-1 = 99.1%; VHR-2 = 98.0%; VHR-3 = 97.9%.

Example 8

5-HB(F)B(F)B(F,F)XB(F,F)-F (1-5-3) 3% 5-BB(F)B(F)B(F,F)XB(F)-F (1-6-1)4% V-HH-V (2-1-1) 15% V-HH-2V (2-1-1) 15% 1V-HH-V (2-1-1) 8% 1V-HH-V1(2-1-1) 5% 1V2-HH-V (2-1-1) 5% 1V2-HH-2V1 (2-1-1) 4% 3-HH-O1 (3-1-1) 3%3-HHEH-5 (3-4-1) 3% 3-HHB-1 (3-5-1) 4% 1-BB(F)B-2V (3-7-1) 5%2-BB(F)B-2V (3-7-1) 5% 1V2-BB-F (4-2-1) 3% 3-HHB-CL (4-4-1) 3%3-BB(F,F)XB(F,F)-F (4-11-1) 15% NI = 70.9° C.; Tc ≦ −20° C.; Δn = 0.099;Δε = 2.9; Vth = 2.46 V; η = 11.3 mPa · s; γ1 = 45.4 mPa · s; τ = 8.6 ms;VHR-1 = 99.0%; VHR-2 = 97.9%; VHR-3 = 98.0%.

Example 9

3-BB(F)B(F,F)XB(F,F)-F (1-2-3) 3% 4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 7%V-HH-V (2-1-1) 10% V-HH-2V (2-1-1) 20% 1V-HH-V (2-1-1) 10% V-HH-3(3-1-1) 15% V2-BB-1 (3-3-1) 4% 1-BB(F)B-2V (3-7-1) 7% 2-BB(F)B-2V(3-7-1) 8% 3-BB(F,F)XB(F,F)-F (4-11-1) 4% 3-HHEB(F,F)-F (4-15-1) 3%3-HBEB(F,F)-F (4-16-1) 3% 1O1-HBBH-5 (—) 3% 3-HHB(F)B(F,F)-F (—) 3% NI =74.3° C.; Tc ≦ −20° C.; Δn = 0.111; Δε = 3.0; Vth = 2.39 V; η = 11.0 mPa· s; γ1 = 44.5 mPa · s; τ = 8.5 ms; VHR-1 = 99.2%; VHR-2 = 98.0%; VHR-3= 98.1%.

Example 10

3-BB(F)B(F,F)XB(F,F)-F (1-2-3) 3% 4-BB(F)B(F,F)XB(F,F)-F (1-2-3) 10%V-HH-V (2-1-1) 10% V-HH-2V (2-1-1) 20% 1V-HH-V (2-1-1) 10% V-HH-3(3-1-1) 18% V2-BB-1 (3-3-1) 4% 1-BB(F)B-2V (3-7-1) 7% 2-BB(F)B-2V(3-7-1) 8% 3-HGB(F,F)-F (4-17-1) 3% 5-GHB(F,F)-F (4-18-1) 4%3-HHBB(F,F)-F (—) 3% NI = 73.8° C.; Tc ≦ −20° C.; Δn = 0.109; Δε = 3.0;Vth = 2.37 V; η = 10.3 mPa · s; γ1 = 42.9 mPa · s; τ = 8.4 ms; VHR-1 =99.0%; VHR-2 = 97.9%; VHR-3 = 97.9%.

The compositions in Examples 1 to 10 had a small rotational viscosity incomparison with those in Comparative Examples 1 to 3. Thus, the liquidcrystal composition of the invention was so much superior incharacteristics to that described in the patent documents Nos. 1 to 5.

The invention provides a liquid crystal composition that satisfies atleast one characteristic among characteristics such as a high maximumtemperature of a nematic phase, a low minimum temperature of a nematicphase, a small viscosity, a large optical anisotropy, a large dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat, or that is suitably balancedregarding at least two of the characteristics. Since a liquid crystaldisplay device that contains the composition provides a AM device havinga short response time, a large voltage holding ratio, a large contrastratio, a long service life and so forth, it cab be used for a liquidcrystal projector, a liquid crystal television and so forth.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the disclosure has beenmade only by way of example, and that numerous changes in the conditionsand order of steps can be resorted to by those skilled in the artwithout departing from the spirit and scope of the invention.

1. A liquid crystal composition having a nematic phase that comprisestwo components, wherein the first component is at least one compoundselected from the group of compounds represented by formula (1), and thesecond, component is at least one compound selected from the group ofcompounds represented by formula (2):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; R² and R³are each independently alkenyl having 2 to 12 carbons; ring A and ring Bare each independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z¹ and Z² are eachindependently a single bond, ethylene, carbonyloxy ordifluoromethyleneoxy; X¹, X², X³ and X⁴ are each independently hydrogenor fluorine; Y¹ is fluorine, chlorine or trifluoromethoxy; and m and jare each independently 0, 1, 2 or 3 and the sum of m and j is 2 or
 3. 2.The liquid crystal composition according to claim 1, wherein the firstcomponent is at least one compound selected from the group of compoundsrepresented by formulas (1-1) to (1-9):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; X¹, X², X³,X⁴, X⁵, X⁶, X⁷, X⁸ and X⁹ are each independently hydrogen or fluorine;and Y¹ is fluorine, chlorine or trifluoromethoxy.
 3. The liquid crystalcomposition according to claim 2, wherein the first component is atleast one compound selected from the group of compounds represented byformula (1-1).
 4. The liquid crystal composition according to claim 2,wherein the first component is a mixture of at least one compoundselected from the group of compounds represented by formula (1-1) and atleast one compound selected from the group of compounds represented byformula (1-2).
 5. The liquid crystal composition according claim 1,wherein the ratio of the first component is in the range ofapproximately 5% to approximately 40% by weight and the ratio of thesecond component is in the range of approximately 20% to approximately95% by weight, based on the total weight of the liquid crystalcomposition.
 6. The liquid crystal composition according to claim 1,wherein the composition further comprises at least one compound selectedfrom the group of compounds represented by formula (3) as a thirdcomponent:

wherein R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; R⁵ is alkylhaving 1 to 12 carbons or alkoxy having 1 to 12 carbons; ring C and ringA are each independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z³ is independently a single bond, ethyleneor carbonyloxy; and p is 1, 2 or
 3. 7. The liquid crystal compositionaccording to claim 6, wherein the third component is at least onecompound selected from the group of compounds represented by formulas(3-1) to (3-11):

wherein R⁴ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; and R⁵ isalkyl having 1 to 12 carbons or alkoxy having 1 to 12 carbons.
 8. Theliquid crystal composition according to claim 7, wherein the thirdcomponent is at least one compound selected from the group of compoundsrepresented by formula (3-1).
 9. The liquid crystal compositionaccording to claim 6, wherein the ratio of the third component is in therange of approximately 5% to approximately 60% by weight based on thetotal weight of the liquid crystal composition.
 10. The liquid crystalcomposition according to claim 1, wherein the composition furthercomprises at least one compound selected from the group of compoundsrepresented by formula (4) as a fourth component:

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; ring E isindependently 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z⁴ is independently asingle bond, ethylene, carbonyloxy or difluoromethyleneoxy; X¹ and X²are each independently hydrogen or fluorine; Y¹ is fluorine, chlorine ortrifluoromethoxy; and k is 1 or
 2. 11. The liquid crystal compositionaccording to claim 6, wherein the composition further comprises at leastone compound selected from the group of compounds represented by formula(4) as a fourth component:

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine; ring E isindependently 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene,2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene,3,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; Z⁴ is independently asingle bond, ethylene, carbonyloxy or difluoromethyleneoxy; X¹ and X²are each independently hydrogen or fluorine; Y¹ is fluorine, chlorine ortrifluoromethoxy; and k is 1 or
 2. 12. The liquid crystal compositionaccording to claim 10, wherein the fourth component is at least onecompound selected from the group of compounds represented by formulas(4-1) to (4-18):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.
 13. Theliquid crystal composition according to claim 11, wherein the fourthcomponent is at least one compound selected from the group of compoundsrepresented by formulas (4-1) to (4-18):

wherein R¹ is alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which arbitrary hydrogen is replaced by fluorine.
 14. Theliquid crystal composition according to claim 12, wherein the fourthcomponent is at least one compound selected from the group of compoundsrepresented by formula (4-11).
 15. The liquid crystal compositionaccording to claim 13, wherein the fourth component is at least onecompound selected from the group of compounds represented by formula(4-11).
 16. The liquid crystal composition according to claim 10,wherein the ratio of the fourth component is in the range ofapproximately 5% to approximately 40% by weight based on the totalweight of the liquid crystal composition.
 17. The liquid crystalcomposition according to claim 11, wherein the ratio of the fourthcomponent is in the range of approximately 5% to approximately 40% byweight based on the total weight of the liquid crystal composition. 18.The liquid crystal composition according to claim 1, wherein the maximumtemperature of a nematic phase is approximately 70° C. or higher, theoptical anisotropy (25° C.) at a wavelength of 589 nm is approximately0.08 or more, and the dielectric anisotropy (25° C.) at a frequency of 1kHz is approximately 2 or more.
 19. A liquid crystal display devicecomprising the liquid crystal composition according to claim
 1. 20. Theliquid crystal display device according to claim 19, wherein anoperating mode of the liquid crystal display device is a TN mode, an OCBmode, an IPS mode or a PSA mode, and a driving mode of the liquidcrystal display device is an active matrix mode.